\begin{tabular}{l*{6}{c}}
\toprule
                    &\multicolumn{1}{c}{1963-1987}&\multicolumn{1}{c}{1963-2016}&\multicolumn{1}{c}{1963-1987}&\multicolumn{3}{c}{1963-2016}         \\\cmidrule(lr){2-2}\cmidrule(lr){3-3}\cmidrule(lr){4-4}\cmidrule(lr){5-7}
                    &\multicolumn{1}{c}{(1)}&\multicolumn{1}{c}{(2)}&\multicolumn{1}{c}{(3)}&\multicolumn{1}{c}{(4)}&\multicolumn{1}{c}{(5)}&\multicolumn{1}{c}{(6)}\\
\midrule
Relative supply of college workers&      -0.806&      -0.317&      -0.737&      -0.555&      -0.816&      -0.632\\
                    &     (0.134)&     (0.058)&     (0.130)&     (0.060)&     (0.083)&     (0.101)\\
\addlinespace
Real minimum wage   &            &            &      -0.221&      -0.307&      -0.257&      -0.132\\
                    &            &            &     (0.068)&     (0.053)&     (0.058)&     (0.047)\\
\addlinespace
Time                &       0.027&       0.014&       0.024&       0.019&            &            \\
                    &     (0.005)&     (0.001)&     (0.005)&     (0.001)&            &            \\
\addlinespace
Constant            &      -0.008&       0.007&       0.008&       0.010&      -0.027&       0.035\\
                    &     (0.017)&     (0.009)&     (0.017)&     (0.009)&     (0.016)&     (0.027)\\
\midrule
Time Polynomial     &           1&           1&           1&           1&           2&           3\\
Observations        &          25&          54&          25&          54&          54&          54\\
\textit{R}-squared  &       0.532&       0.912&       0.694&       0.941&       0.949&       0.972\\
\bottomrule
\end{tabular}
